Water distribution systems employing rotating nozzles to broadcast water over an area have a number of uses. One use is to effectively irrigate a wide circular zone by means of a sprinkler system. A less common use is for cleaning purposes, whereby the nozzles would be directed more in a focused spray pattern. In both cases, however, it is useful to control the speed of nozzle rotation. In the cleaning example, a slower speed produces a greater impact to the target surface because less of the flow is directed obliquely. The greater impact produces a greater force for dislodging dirt. In the sprinkler case, a slower speed produces a larger broadcast area because, in a similar manner, more of the spray is thrown outwardly and less in a radial direction. An additional benefit of speed control is the prolonged life of the moving parts of the system through the reduction of wear and tear.
In the typical rotating nozzle system, one or more nozzles are placed at distance from an axis of rotation creating a moment arm. As water is forced through the orifice of the nozzle, the reaction force produces torque which propels the spin. The more the stream of water is directed tangentially to the rotational circumference, the greater the torque. One way to reduce the torque, and thereby to control the angular speed, is to direct the stream more upwardly. More upward vectoring serves the cleaning application, and more outwardly upward, the sprinkler circumstance. In both cases, additional friction caused by the downward force component contributes not only to a speed reduction by virtue of friction, but also to system wear and degradation by the same agent.
Controlling the torque by redirecting the spray stream, however, does not compensate for variable water pressure. Supplemental control means have been sought and are present in the prior art. In U.S. Pat. No. 0,270,664 to Henderson, for example, a baffle is placed so as to deflect the stream exiting a nozzle. Doing so diminishes the reaction force and slows the spin. The baffle can be bent to incline more or less into the stream, thereby providing a manual adjustment means. U.S. Pat. No. 2,021,710 to Wilson teaches an oscillating vane placed in the path of one of the nozzles. The speed of rotation can be adjusted by adjusting the amplitude of the oscillation.
In both of the above prior art examples, the control means has to be readjusted with each fluctuation of water pressure due to line pressure surges or other events, such as clogging nozzle ports. In U.S. Pat. No. 3,979,066 to Fortner, the baffle is initially placed out of range of the water stream until a certain speed is reached at which the baffle begins to intersect the inwardly-spiraling water path. In a sense, Fortner's device is self-governing, but only partially so. While it begins braking automatically at a pre-determined angular velocity, it becomes dependent upon manual adjustment thereafter to maintain a constant speed under variable pressure conditions.
What is missing in the prior art is an automated means of controlling angular speed responsive to pressure fluctuations. Such a means would have an equilibrium state whereby a tendency for higher speed would be balanced with a greater resistance, and visa versa for lower speed.